Electrode boilers

ABSTRACT

An electrode steam boiler comprises a water-receiving shell, water-heating electrodes supported in the shell, a pump for supplying feed water to the shell, means for causing intermittent operation of the pump, and means for withdrawing water from the shell just before and/or during and/or just after at least some of the periods of operation of the pump, so that water withdrawal occurs when the concentration of salts in the boiler water is highest.

United States Patent 91 1 Williams Sept. 25, 1973 ELECTRODE BOILERS3,512,507 5 1970 Dixon 122 382 [76] Inventor: Stanley Austen Williams,10 g g l D riston Rd Parkstone oo e iggins u 3,682,141 8/1972 Johansenl22/382 Dorset, England [22] Filed: Nov. 16, 1971 PrimaryExaminer-Kenneth W. Sprague [211 pp No: 199,187 Attorney-Michael S.Striker 30 F A r A [57] 7 ABSTRACT 1 or'elgn pp Pllwnty Data Y Anelectrode steam boiler comprises a water-receiving 3Q, 1 70 grga tgritainn .57j2/7 O shell, water-heating electrodes supported in theshell, a pump for supplying feed water to the shell, means for [52 US.Cl. 122/382 causing intermittent operation of the pump, and means [51]Int. Cl. F22b 37/54 for withdrawing water from the shell just beforeand/or [58] Field of Search 122/379, 382 during and/or just after atleast some of the periods of operation of the pump, so that waterwithdrawal occurs [56] References Cited when the concentration of saltsin the boiler water is UNITED STATES PATENTS highest- 3,269,364 8/1966Higgins .l 122/379 15 Claims, 1 Drawing Figure 1 ELECTRODE BOILERS Thisinvention relates to an electrode boiler for generating steam,hereinafter referred to as an electrode steam boiler, and to a method ofoperating such a boiler.

In electrode steam boilers it is usually necessary to control theconcentration of salts contained in the feed water, particularly in thewater surrounding the electrodes. A method of doing this is to removewater periodically from the boiler shell by means of a pipe which passesthrough the boiler shell and withdraws water from any desired region ofthe shell and advantageously from a region at or near the level of thelower end of the electrodes. The amount of water withdrawn by such apipe must be controlled, and this is often done by providing it with anelectrically-operated valve which can be operated by a timing device sothat, at certain fixed intervals of time, water is withdrawn from theboiler shell and passed to waste. Alternatively, the operation of thevalve can be controlled by some, form of conductivity meter.

Operating the valve by means of a timing device has the disadvantagethat the same amount of water is withdrawn irrespective of the load atwhich the boiler is operating or the concentration of salts in it.Operation of the valve by means of a conductivity meter is, for varioustechnical reasons, very difficult to keep functioning all the time andis therefore very seldom used.

According to one aspect of the present invention in a method ofoperating an electrode steam boiler of the kind comprising electrodessupported in the boiler,

.means for withdrawing water from the boiler and means for supplyingfeed water to the boiler the feed water is supplied to the boilerintermittently and water is withdrawn intermittently from the boilerjust before and/or during and/or just after at least some of theintervals of feed water supply.

Preferably, each period of water withdrawal from the boiler endsimmediately before the commencement of an interval of feed water supplyso that water withdrawal occurs when the concentration of salts in theboiler water is highest.

Preferably, the quantity of water withdrawn during each withdrawalperiod is set to a predetermined value, which value is adjustable.

in an electrode steam boiler in which no water is withdrawn and the feedwater is supplied at intervals, the frequency of the feed water supplyintervals will be proportional to the concentration of salts in theboiler water and to the amount of steam being generated. In an electrodesteam boiler operating according to the method of the present invention,therefore, it will be appreciated that water is withdrawn from theboiler at a frequency which is proportional to the concentration ofsalts in the boiler.

According to a further aspect of the invention, an electrode steamboiler comprises a water-receiving shell, watenheating electrodessupported in the shell, a pump for supply feed water to the shell, meansfor causing intermittent operation of the pump, and means forwithdrawing water from the shell just before and/or during and/or justafter at least some of the periods of operation of the pump.

The means for withdrawing water from the shell may be a pipe connectedto the shell, or passing through the shell wall into the interior of theshell, and valve means controlling the flow of water through said pipe.The valve means may be electrically operated, opening and closing of thevalve means being effected in timed relationship with the intermittentoperation of the feed water pump. For example, the means for causingintermittent operation of the feed water pump may comprise an adjustableelectric timer and the latter may be arranged to open said valve meansfor a pre-set period prior to each intermittent operation of the feedwater pump. Preferably, the timer would be arranged to close said valvemeans prior to initiating an operation of the feed water pump.

The accompanying drawing is a schematic view of an electrode steamboiler in accordance with the invention.

The electrode steam boiler shown in the drawing has a shell 1 in whichthree electrodes 2, 3, 4 are supported and connected by leads 5 to athree-phase A.C. supply network 6. A pump 7 driven by an electric motor8 is arranged to supply feed water to the shell 1 via a pipe 9 from asuitable water source (not shown). The motor 8 is connected to thenetwork 6 via a switch 10.

An electric timer 11 is connected to the network 6 and is controlled bysignals received from a controller 12. The latter is supplied withcurrent from a current transformer 13 which measures the current flowingin one of the electrode supply leads 5. As the water level in the shell1 drops, due to generation of steam, the current in the leads 5 willdecrease and therefore the current supplied to the controller 12 by thetransformer 13 will also decrease. Decrease of the latter current to apredetermined value indicates that feed water should be supplied to theshell 1 to make up for the loss of water caused by the generation ofsteam. When this predetermined current flows to the controller 12, asignal is sent by the controller to initiate operation of the timer 11as described more fully hereinafter.

A water outlet pipe 14 is connected to the shell 1 and is provided withan electrically-operated valve 15. The numeral 16 designates the outletpipe for steam generated in the shell 1.

. When the controller 12 sends a signal to the timer 1 1 indicating theneed for water to be supplied to the shell 1, the timer first sends animpulse to the valve 15 and the latter is opened for a predeterminedinterval of time (which interval is adjustable at the timer) to allowwater to flow from the shell through the pipe 14. When the valve 15closes at the end of this predetermined interval of time, the timer 11sends a further impulse to a solenoid 17 which closes the switch 10 tooperate the pump 7 and supply the feed water to the shell. As the waterlevel builds up in the shell, the current supplied to the controller 12increases and at a predetermined value of this current the controller 12sends a signal to the timer 11 to initiate de-energisation of thesolenoid 17 so that the switch 10 re-opens to stop the pump 7.

In the embodiment of the invention described above, the pipe 14 is shownas being connected to the wall of the shell 1. If desired the pipe 14may extend through the wall of the shell 1 and extend into the latter,for example as indicated by the dotted lines 14a, to a region adjacentthe lower ends of the electrodes 2, 3 and 4. In yet another embodiment,the pipe 14 may be connected to the feed water supply pipe 9, asindicated by the dotted line 14b.

Again, the feed water supply pipe 9 is shown as being connected to theshell 1, but if desired this pipe may feed water to jets arranged todirect the incoming water into spaces between the electrodes asdescribed in US. Patent Application Ser. No. 106128 filed Jan. 13th 1971entitled Improvements in and relating to electrode boilers.

What is claimed is:

l. A method of cyclically operating an electrode steam boiler of thetype comprising electrodes supported in the interior of the boiler andmaintained at least partly immersed in the water in said boiler for atleast a portion of a boiler operating cycle and extending into the waterin said boiler in direction transverse to the plane of the water levelin said boiler, comprising the steps of monitoring the magnitude of thecurrent flowing through at least one of said electrodes while saidelectrodes are partly immersed in the water in said boiler to indirectlymonitor the lowering of the water level in said boiler resulting fromthe conversion of the water in said boiler into steam; feedingadditional water into said boiler beginning at a time after themagnitude of said current has fallen to a predetermined first value as aresult of the fall of the water level to a predetermined first level dueto the conversion of the water in said boiler into steam and only untilthe magnitude of said current rises to a predetermined second valueindicative of a rise of the water level in said boiler to apredetermined second level higher than said first level; withdrawingwater from the boiler beginning at a time after the magnitude of saidcurrent has fallen to said predetermined first value but not during saidfeeding of additional water; and terminating said withdrawing of waterbefore the magnitude of said current again falls to said predeterminedfirst value.

2. A method as defined in claim 1, wherein said step of feedingadditional water consists of effecting a single uninterrupted feeding ofwater terminating when the magnitude of said current reaches said secondvalue.

3. A method as defined in claim 1, wherein said step of withdrawingwater consists of effecting a single uninterrupted withdrawal of water.

4. An arrangement comprising an electrode'steam boiler of the typecomprising electrodes supported in the interior of the boiler andmaintained at least partly immersed in water contained in said boilerfor heating such water and extending into the water in said boiler indirection transverse to the plane of the water level in said boiler;monitoring means for monitoring the magnitude of the current flowingthrough at least one of said electrodes while said electrodes are partlyimmersed in the water in said boiler to indirectly monitor the loweringof the water level in said boiler resulting from the conversion of thewater in said boiler into steam; feeding means operatively associatedwith said monitoring means and operative for feeding additional waterinto said boiler beginning at a time after the magnitude of said currenthas fallen to a predetermined first value as a result of the fall of thewater level to a predetermined first level due to the conversion of thewater in said boiler into steam and operative for effecting such feedingof additional water only until the magnitude of said current rises to apredetermined second value indicative of a rise of the water level insaid boiler to a predetermined second level higher than said first valueand only until a time before the magnitude of said current again fallsto said predetermined first value.

5. An electrode steam boiler comprising a waterreceiving shell,water-heating electrodes supported in said shell, means for supplyingcurrent to said electrodes, a pump for supplying feed water to saidshell, means for monitoring the current supplied to at least one of saidelectrodes, means controlled by said monitoring means for starting saidpump during a period commencing after said current falls below a firstpredetermined value and for subsequently stopping the pump when thecurrent subsequently rises to a second and higher predetermined value,and further means controlled by said monitoring means for withdrawingwater from the shell in a period following the fall of the current tosaid first predetermined value during which the feed water pump isinoperative.

6. A method of cyclically operating an electrode steam boiler of thetype comprising electrodes supported in the interior of the boiler andmaintained at least partly immersed in the water in said boiler for atleast a portion of a boiler operating cycle and extending into the waterin said boiler in direction transverse to the plane 'of the water levelin said boiler, comprising the steps of monitoring the magnitude of thecurrent flowing through at least one of said electrodes while saidelectrodes are partly immersed in the water in said boiler to indirectlymonitor the lowering of the water level in said boiler resulting fromthe conversion of the water in said boiler into steam; feedingadditional water into said boiler beginning at a time after themagnitude of said current has fallen to a predetermined first value as aresult of the fall of the water level to a predetermined first level dueto the conversion of the water in said boiler into steam and only untilthe magnitude of said current rises to a predetermined second valueindicative of a rise of the water level in said boiler to apredetermined second level higher than said first level; withdrawingwater from the boiler beginning at a time after the magnitude of saidcurrent has fallen to said predetermined first value and terminatingsaid withdrawing of water before the magnitude of said current againfalls to said predetermined first value.

7. The method claimed in claim 6, in which each period of waterwithdrawal from the boiler ends immediately before the commencement ofan interval of feed water supply, so that water withdrawal occurs whenthe concentration of salts in the boiler water is highest.

8. The method claimed in claim 6, in which the quantity of waterwithdrawn during each withdrawal period is set to a predetermined value,which value is adjustable.

9. The method claimed in claim 6, in which the water is withdrawn from aregion in the boiler adjacent to the lower ends of the electrodes.

10. A boiler as claimed in claim 5, in which the means for withdrawingwater from said shell is a pipe connected to said shell and valve meanscontrolling the flow of water through said pipe.

11. A boiler as claimed in claim 5, in which the means for withdrawingwater from said shell is a pipe passing through the shell wall into theinterior of said shell and valve means controlling the flow of waterthrough said pipe.

12. A boiler as claimed in claim 10, in which said valve means iselectrically operated, opening and closing of said valve means beingeffected in timed relation- '5 ship with the intermittent operation ofsaid feed water pump. l

13. A boiler as claimed in claim 12, in which said monitoring meanscomprises an adjustable electric timer arranged to open said valve meansfor a pre-set period prior to each period of operation of said feedwater pump, and to close said valve means prior to initiating operationof said feed water pump.

14. A boiler as claimed in claim 11, in which said valve means iselectrically operated, opening and clostiating an operation of said feedwater pump.

III l I. III

1. A method of cyclically operating an electrode steam boiler of thetype comprising electrodes supported in the interior of the boiler andmaintained at least partly immersed in the water in said boiler for atleast a portion of a boiler operating cycle and extending into the waterin said boiler in direction transverse to the plane of the water levelin said boiler, comprising the steps of monitoring the magnitude of thecurrent flowing through at least one of said electrodes while saidelectrodes are partly immersed in the water in said boiler to indirectlymonitor the lowering of the water level in said boiler resulting fromthe conversion of the water in said boiler into steam; feedingadditional water into said boiler beginning at a time after themagnitude of said current has fallen to a predetermined first value as aresult of the fall of the water level to a predetermined first level dueto the conversion of the water in said boiler into steam and only untilthe magnitude of said current rises to a predetermined second valueindicative of a rise of the water level in said boiler to apredetermined second level higher than said first level; withdrawingwater from the boiler beginning at a time after the magnitude of saidcurrent has fallen to said predetermined first value but not during saidfeeding of additional water; and terminating said withdrawing of waterbefore the magnitude of said current again falls to said predeterminedfirst value.
 2. A method as defined in claim 1, wherein said step offeeding additional water consists of effecting a single uninterruptedfeeding of water terminating when the magnitude of said current reachessaid second value.
 3. A method as defined in claim 1, wherein said stepof withdrawing water consists of effecting a single uninterruptedwithdrawal of water.
 4. An arrangement comprising an electrode steamboiler of the type comprising electrodes supported in the interior ofthe boiler and maintained at least partly immersed in water contained insaid boiler for heating such water and extending into the water in saidboiler in direction transverse to the plane of the water level in saidboiler; monitoring means for monitoring the magnitude of the currentflowing through at least one of said electrodes while said electrodesare partly immersed in the water in said boiler to indirectly monitorthe lowering of the water level in said boiler resulting from theconversion of the water in said boiler into steam; feeding meansoperatively associated with said monitoring means and operative forfeeding additional water into said boiler beginning at a time after themagnitude of said current has fallen to a predetermined first value as aresult of the fall of the water level to a predetermined first level dueto the conversion of the water in said boiler into steam and operativefor effecting such feeding of additional water only until the magnitudeof said current rises to a predetermined second value indicative of arise of the water level in said boiler to a predetermined second levelhigher than said first level; and withdrawing means operativelyassociated with said monitoring means and operative for withdrawingwater from said boiler beginning at a time after the magnitude of saidcurrent has fallen to said first value and only until a time before themagnitude of said current again falls to said predetermined first value.5. An electrode steam boiler comprising a water-receiving shell,water-heating electrodes supported in said shell, means for supplyingcurrent to said electrodes, a pump for supplying feed water to saidshell, means for monitoring the current supplied to at least one of saidelectrodes, means controlled by said monitoring means for starting saidpump during a period commencing after said current falls below a firstpredetermined value and for subsequently stopping the pump when thecurrent subseQuently rises to a second and higher predetermined value,and further means controlled by said monitoring means for withdrawingwater from the shell in a period following the fall of the current tosaid first predetermined value during which the feed water pump isinoperative.
 6. A method of cyclically operating an electrode steamboiler of the type comprising electrodes supported in the interior ofthe boiler and maintained at least partly immersed in the water in saidboiler for at least a portion of a boiler operating cycle and extendinginto the water in said boiler in direction transverse to the plane ofthe water level in said boiler, comprising the steps of monitoring themagnitude of the current flowing through at least one of said electrodeswhile said electrodes are partly immersed in the water in said boiler toindirectly monitor the lowering of the water level in said boilerresulting from the conversion of the water in said boiler into steam;feeding additional water into said boiler beginning at a time after themagnitude of said current has fallen to a predetermined first value as aresult of the fall of the water level to a predetermined first level dueto the conversion of the water in said boiler into steam and only untilthe magnitude of said current rises to a predetermined second valueindicative of a rise of the water level in said boiler to apredetermined second level higher than said first level; withdrawingwater from the boiler beginning at a time after the magnitude of saidcurrent has fallen to said predetermined first value and terminatingsaid withdrawing of water before the magnitude of said current againfalls to said predetermined first value.
 7. The method claimed in claim6, in which each period of water withdrawal from the boiler endsimmediately before the commencement of an interval of feed water supply,so that water withdrawal occurs when the concentration of salts in theboiler water is highest.
 8. The method claimed in claim 6, in which thequantity of water withdrawn during each withdrawal period is set to apredetermined value, which value is adjustable.
 9. The method claimed inclaim 6, in which the water is withdrawn from a region in the boileradjacent to the lower ends of the electrodes.
 10. A boiler as claimed inclaim 5, in which the means for withdrawing water from said shell is apipe connected to said shell and valve means controlling the flow ofwater through said pipe.
 11. A boiler as claimed in claim 5, in whichthe means for withdrawing water from said shell is a pipe passingthrough the shell wall into the interior of said shell and valve meanscontrolling the flow of water through said pipe.
 12. A boiler as claimedin claim 10, in which said valve means is electrically operated, openingand closing of said valve means being effected in timed relationshipwith the intermittent operation of said feed water pump.
 13. A boiler asclaimed in claim 12, in which said monitoring means comprises anadjustable electric timer arranged to open said valve means for apre-set period prior to each period of operation of said feed waterpump, and to close said valve means prior to initiating operation ofsaid feed water pump.
 14. A boiler as claimed in claim 11, in which saidvalve means is electrically operated, opening and closing of said valvemeans being effected in timed relationship with the intermittentoperation of said feed water pump.
 15. A boiler as defined in claim 14,in which said monitoring means comprises an adjustable electric timerarranged to open said valve means for a pre-set period prior to eachperiod of operation of said feed water pump, and to close said valvemeans prior to initiating an operation of said feed water pump.